Method for the processing of potassium containing materials

Abstract

A method for the processing of potassium containing materials comprises:(i) Separation of a potassium containing mineral from gangue minerals;(ii) Acid leaching whereby substantially all potassium, iron, aluminum and magnesium is solubilized and mixed potassium / iron double salt formed;(iii) Selectively crystallizing the mixed potassium / iron double salt formed in the leach step (ii);(iv) Second separation to separate the mixed potassium / iron double salt formed in step (iii);(v) Thermal decomposition to produce an iron oxide, a potassium salt and one or more phosphates;(vi) Leaching the product of the thermal decomposition;(vii) Third separation to separate the iron oxide and phosphate from the potassium salt;(viii) Recovering the potassium salt by crystallization;(ix) Separating the iron oxide and phosphate of step (vii) by leaching and subsequent solid liquid separation; and(x) Precipitating phosphate from liquor produced in step (ix) through the addition of a base.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a 371 U.S. National Stage of International Application No. PCT / AU2015 / 000691, filed Nov. 16, 2015, and published in English as WO 2016 / 077864 A1 on May 26, 2016, which claims the benefit of and priority to Australian Patent Application No. 2014904601, filed Nov. 17, 2014. The entire disclosures of the above applications are incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to a method for the processing of potassium containing materials. More particularly, the method of the present invention is intended for use in the recovery of at least potassium as a saleable product from potassium rich minerals including, but not limited to, glauconitic greensand. The method of the present invention may further recover one or more of iron, magnesium and aluminium from those same minerals.BACKGROUND ART[0003]The major sources of commercially mined potash have historically come from large sylv...

AI Technical Summary

Benefits of technology

[0028]Preferably, the KFe(SO4)2 may be washed to remove entrained impurities, such as Al2(SO4)3, with a saturated solution of K2SO4, K and Mg sulfates, K2SO4 / Fe2(SO4)3, H2SO4 or water. The wash solution may be recycled to the KFe(SO4)2 crystallisation stage. The wash filtrate is preferably recycled to the KFe(SO4)2 crystallisation stage in which the K / Fe ratio in the liquor will increase and result in a higher iron recovery if the wash liquor contains a high K / Fe ratio. The amount of recycled K2SO4 can be controlled to target a specific Fe recovery.

[0029]Still preferably, the crystallisation step (iv) may be achieved by forced cooling of the mixed KFe(SO4)2, MgSO4 and phosphate crystallisation filtrate to between about 20 to 60° C., for example to about 60° C. The reduction in temperature from that of the KFe(SO4)2 crystallisation stage initiates Al2(SO4)3 crystallisation. The crystals may be recovered by filtration and washed with water or a solution containing Al2(SO4)3. The Al2(SO4)3 is dried and stored for sale as Al2(SO4)3 with varying degree of hydration. In this manner an expensive K-alum decomposition stage is avoided.

Problems solved by technology

To date there has been no commercial production of potash fertilisers from glauconite rich deposits.

Due to a variety of circumstances, each attempt has been commercially unsuccessful.

Whilst there have been several flow sheets for the recovery of potassium from these leach liquors proposed, all have proven commercially un-economic.

This process suffered in particular from high energy costs as a result of the K-alum calcination stage.

The recovery of K2SO4 from K-alum results in a similar fate to that of the Moxham process described above as it requires an expensive calcination step to convert K-alum to K2SO4, Al2O3 and SO3.

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